Knee braces and braces for other joints are commonly employed after surgery or for treatment of injury to the joint. Such braces generally serve two major purposes. First, they brace or stabilize the joint in order generally to control its movement. Second, they limit joint flexion and/or extension in a controllable and adjustable fashion to prevent reinjury of the knee and to promote therapeutic and rehabilitation objectives.
Many braces have been devised to stabilize the knee and other joints and anatomical structures about various axes. Hinges which limit flexion and extension of the joint, such as those according to the present invention, may be employed, as a general matter, with or in any of such devices.
Bracing hinges for controllably limiting flexion and extension of the knee generally fall within one or more of several categories. A first category includes bicentric hinges in which a thigh bar and a calf bar of the brace couple to each other via a hinge which features two pivot points. Such braces have been said to replicate more accurately the motion of the knee joint, in which the condyles of the femur do not rotate relative to the tibial plateau about a fixed axis. (Instead, such braces seek to emulate changes in location of the instantaneous center of rotation of the tibia with respect to the femur as a function of the flexion angle.) Rotation (flexion and/or extension) of the thigh and calf bars relative to each other in these bicentric hinges is limited or controlled using members such as adjustably positionable rotatable cams (see, e.g., U.S. Pat. No. 4,554,913 to Womack, et al. which is incorporated herein by this reference), or interlocking teeth forming a portion of or connected to the thigh and calf bars which govern their position relative to each other. These devices have been constrained in flexion and extension in many ways, including use of gears and other structure (see, e.g., U.S. Pat. No. 4,697,583 to Mason, et al., U.S. Pat. No. 4,732,143 to Kansek, et al. and U.S. Pat. No. 5,060,640 to Rasmusson, all of which are incorporated herein by this reference).
A second general category of knee brace hinges employs a monocentric rather than a bicentric approach. The thigh and calf bars of the brace are coupled via a hinge which includes only one pivot point about which the thigh and calf bars pivot relative to one another. A number of conventional braces employ such monocentric hinges. These in turn often include structure for adjusting the limits to which the thigh and calf bars may rotate relative to one another, both in flexion and extension of the knee. For instance, U.S. Pat. No. 5,460,599 to Davis, et al., which is incorporated by this reference, employs rotatably positionable members with teeth and arcuate slots to receive and limit travel of pins which connect to the thigh and calf bars in order to limit their rotation relative to each other. U.S. Pat. No. 4,982,732 to Morris, which is incorporated by this reference, includes a generally circular housing that mounts a number of discrete sliding structures positioned at ten degree intervals on the housing. The sliding structures may be actuated or deactuated as desired to control flexion and extension of the brace and knee. U.S. Pat. No. 5,000,169 to Swicegood, which is incorporated by this reference, discloses a hinge which controls flexion and extension of the knee using a generally circular base whose periphery contains a number of indentations into which corresponding structure may be interposed to create limits on flexion and extension of the brace and knee. Other hinges employ generally circular plates coupled to the thigh and/or calf members. These plates feature a number of holes or indentations disposed at desired angular positions and into which pins, keys or similar structure may be placed in order to govern flexion and extension of the brace and knee. These conventional monocentric hinges generally incorporate designs that aim to limit patient access to or control over flexion, extension or fixation adjustments.
More recently, U.S. Pat. No. 5,672,152 shows a hinge for an orthopedic brace whose range of rotation may be adjusted by the user. The hinge features a rotation limiting stop provided at the peripheral edge of certain hinge members. The stop is selectively positionable in rotation limiting notches in the members to define an adjustable range of rotation. It can also lock the hinge against rotation in a locked mode of operation. A biasing assembly biases the stop in a radially inward direction to retain the stop in a selected position, but allows elastic radial displacement of the stop in a radially outward direction when a radially outward displacement force is externally applied to the stop. The notched peripheral hinge members of such hinges are exposed, however, and can catch or inadvertently be jammed by foreign objects or clothing which creates a potential for inadvertent operation of the hinge in a mode other than that corresponding to where the stops are placed. Additionally, the stops, which do not feature a positive locking action, can inadvertently catch and change position which again creates the potential of the hinge operating at limits other than those intended.
As post-operative procedures and rehabilitation procedures change and progress, the inventors have noted an increasing need for post-operative and rehabilitation braces which allow users to change and control flexion, extension or fixation of the relevant joint in intuitive and convenient fashion, yet which ensure that the braces maintain their proper limits. Various exercises prescribed in physical therapy, for instance, require the user to change the flexion and extension limits of the knee brace during a physical therapy session or workout. Braces whose hinges inhibit such adjustment typically degrade the effectiveness of such therapy, because patients sometimes simply do not bother to put themselves to the time or trouble necessary to manipulate pins, stops, thumb wheels or other sometimes cumbersome features which have conventionally been employed to adjust and control flexion and extension limits on braces of this sort. Yet such adjustability should not compromise the ability of the hinge to maintain proper limits and function effectively despite inadvertent shock or contact with clothing or foreign objects.